The present invention relates to seals, often referred to as gaskets, for making a fluid or gas tight sealed joint between opposed parallel surfaces.
More particularly, the present invention relates to metal seals which provide plastic deformation to achieve extraordinarily low leak rates between substantially planar parallel surfaces.
A commonly used sealing ring is circular and has a radial cross-section of a xe2x80x9cCxe2x80x9d shape. These xe2x80x9cC sealsxe2x80x9d are constructed both with the open side of the C construction facing the center of the ring such as described in U.S. Pat. No. 5,354,072, and with the open side of the C facing away from the center of the ring. As two parallel surfaces are brought together with the C seal in the middle, the C seal is compressed with the open side of the C cross-section closing during compression. The ductile properties of the seal permit plastic deformation to occur without damaging the mating surface. To increase the elastic recovery of the seal, some C seals are provided with a circular elastic helical spring concentrically located within the center of the seal which also alters the compression resistance and elasticity properties to that desired for particular sealing assemblies. Unfortunately, it is relatively complicated to manufacture a C seal having an internal helical spring resulting in the construction of acceptable seals being typically non-repeatable.
Some C seals are provided with a circular ridge, also referred to in the art as a xe2x80x9cdeltaxe2x80x9d, formed on the surfaces that come in contact with the opposed parallel surfaces which are intended to be sealed. These ridges lessen the initial contact area between the seal and the parallel opposing surfaces thereby requiring less load to plastically deform the seal to accommodate minor distortions in the parallel surfaces. Unfortunately, C seals with these circular ridges often form a chamber between the circular ridge and the outer surface of the C seal as the seal is compressed. Though this seal may be leakproof, or have a leak of a sufficiently low value as to be within tolerances, a xe2x80x9cvirtual leakxe2x80x9d is created if there is a leak between this cylindrical chamber and the interior passage of the seal, thereby permitting gases or liquids to flow slowly therebetween. Though a leakproof seal is in effect, testing of the seal may erroneously and undesirably reflect that a leak exists, and this condition is therefore referred to as a xe2x80x9cvirtual leakxe2x80x9d.
An additional seal which has been available is often referred to as a xe2x80x9cV sealxe2x80x9d which is also circular but instead of having a xe2x80x9cCxe2x80x9d cross-section, the V seal has a V cross-section with the low point of the V constructed to point either inwardly or outwardly towards the center of the seal. Though this construction typically provides for sufficient deformation, the V seal does not typically provide particularly good elastic recovery or repeatability as the point of the V seal forms a stress raiser concentrating the compression loads and making the seal prone to failure upon repeated compressions and decompressions of the seal.
Additional seals in the art include xe2x80x9cZ sealsxe2x80x9d and simple xe2x80x9cO ringsxe2x80x9d. However, each of these seals also suffer for significant disadvantages.
It would thus be desirable to provide an improved ring seal for providing a sealed joint between axially opposed parallel surfaces which has a high degree of resilience, also known as rebound. More particularly, it would be desirable that the ring seal substantially return to its original dimensions after having undergone release from a predetermined compressive force.
It would also be desirable to provide an improved ring seal which can undergo a substantial amount of cycles of compression and decompression and thereafter still provide a substantially leakproof seal.
Moreover, it would be desirable to provide an improved ring seal which is not prone to exhibiting a virtual leak.
In addition, it would be desirable to provide a ring seal for universal applications which can thus be constructed in a variety of sizes and dimensions.
The present invention addresses the aforementioned disadvantages by providing an improved ring seal. The ring seal, similar to previous ring seals, includes an annular shaped body element having an axially aligned hole for gas or fluid passage. The ring seal also includes a radial inner surface, radial outer surface and first and second axially end surfaces which are intended to engage the opposing parallel surfaces between which the sealing joint is intended to be located.
The ring seal of the present invention further includes a plurality of bores projecting inwardly from the ring seal""s radial outer surface toward the ring seal""s center. The formation of the bores creates a plurality of sidewalls extending radially the length of the bore and axially between the ring seal""s axial end surfaces. The plurality of bores may take any number of configurations. For example, preferably the bores are constructed by drilling radially from the ring seal""s radial outer surface toward the ring seal""s center to minimize costs and reduce any difficulties in manufacturing. Bores constructed in this manner have a circular cross-section. However, the bores may also be substantially rectangular in configuration forming substantially planar sidewalls extending axially between the ring seal""s axial end surfaces and radially between the ring seal""s inner and outer radial surfaces. In an alternative preferred embodiment, these planar sidewalls are constructed at an angle with respect to the axis of the ring seal, thus forming openings on the ring seal""s radial outer surface in the form of a parallelogram.
For simplicity, the bores will primarily be described herein as having a circular cross-section though the bores may have cross-sections of other shapes without departing from the spirit or scope of the invention. The number of bores and their diameter may vary depending on the desired mechanical properties of the sealing assembly. For example, an increase in the number of bores or increase in the diameter of the bores causes a corresponding decrease in the thickness of the ring seal""s internal sidewalls which will alter the mechanical characteristics of the seal, including increasing the seal""s ability to deform. However, this increase in the number of bores or increase in the bores"" diameter may diminish the elastic recovery (rebound) of the seal after compression and decompression. In a preferred embodiment, the bores are cylindrical and have diameters of between 25% and 75% of the thickness of the ring seal. Diameters less than 25% will significantly reduce the ring seal""s ability to elastically deform. Meanwhile, increasing the diameter of the bores beyond 75% of the thickness of the ring seal will weaken the structural integrity of the seal and make the seal prone to failure during compression. In a preferred embodiment of the invention, the bores have a diameter of approximately 50% of the thickness of the ring seal.
In a preferred embodiment, the ring seal includes between ten and one hundred fifty bores, thereby forming a corresponding ten to one hundred fifty radially extending sidewalls constructed between the axial end surfaces. In an even more preferred embodiment, the ring seal of the present invention includes between twenty and thirty bores, thereby forming a corresponding twenty to thirty radially and axially extending sidewalls.
The ring seal of the present invention also includes circular ridges which project axially from the axial end surfaces. These circular ridges, also referred to as xe2x80x9cdeltasxe2x80x9d by those skilled in the art, divide the axial end surfaces into inner axial end surfaces and outer axial end surfaces, with the respective inner axial end surfaces being concentrically located within the outer axial end surfaces and thus closer to the ring seal""s center. Of importance, the inner axial end surfaces are offset axially with respect to the outer axial end surfaces. More particularly, the inner axial end surfaces are recessed with respect to the outer axial end surfaces such that the thickness of the ring seal measured at the inner axial end surfaces is thinner than the thickness of the ring seal as measured at the outer axial end surfaces. Providing offset axial end surfaces eliminates the seal""s propensity to form a virtual leak by impeding the ability of the inner axial end surfaces to engage the opposed parallel surfaces during compression.
It is thus an object of the present invention to provide very repeatable, high quality, inexpensive and reliable ring seals for providing a seal between two planar surfaces.
It is an additional object of the present invention to provide a ring seal which provides significant ductility to provide a substantially leakproof seal.
It is still an additional object of the present invention to provide a ring seal which provides substantial elastic recovery so that the seal can undergo substantial amounts of cycles, compression and decompression, and still provide a substantially leakproof seal.
It is still another object of the present invention to provide a ring seal which does not form a concentric chamber when compressed to create a seal that exhibits the characteristics of a virtual leak.
Moreover, it is an object of the present invention to provide a ring seal which is simple to manufacture and which can be constructed in a variety of sizes and dimensions.
These and other features and advantages of the present invention will be appreciated by those skilled in the art from the following detailed description taken in conjunction with the drawings.